a difficult phys question(10)

By Netwon's First Law, an object on the cenveyor belt tends to stay at its state of rest when the belt moves.

If the belt is moving to the right, to an observer on the belt, the objects is moving to the left. Since friction always opposes motion, the frictional force thus acts on the object to the right.

Just imagine that if the conveyor belt is perfectly smooth, there is no friction acting on the object. The object would stay at its original position even the conveyor belt underneath it is moving. Then to an observer on the belt, the object appears to move away him.

我都唔係好清楚你係唔係問緊我答嗰D嘢....但係我試吓答你啦......
其實你首先應該畫噃一幅free-body diagram先....你會發現其實佢除咗friction係冇任何橫向嘅force去令佢向右行......
咁既然條運輸帶唔平滑....咁佢一郁嗰時就會同個行你之間有friction.....但係請注意一件事.......行李唔郁嗰時佢係冇friction....因為個行李冇理由喺有friction但係冇其他同佢方向相反嘅力之下而唔郁架.........
順帶一提......如果你喺條運輸帶上面推嗰件行李....佢會當你俾個力大過佢個maximum friction嗰時至會郁...如果你俾嗰個力細過 max friction......你俾幾多..friction就係幾多....所以冇net force+ remains at rest.....
希望幫到你...

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